Antibacterial Ants!

Ants are undoubtedly one of the most successful creatures on the planet, with 10,000 of them for every human being. Working and cooperating effectively just like a human army, they are present on every single continent except Antarctica. (Some of their bites are even said to be as painful as a bullet shot.) And a reason for their success is: they are antibacterial.

Image from http://en.m.wikipedia.org/wiki/Metapleural_gland

Ants have what is known as a metapleural gland, as seen in the red box in the image. From there, they excrete a secretion that is both antibacterial and antifungal onto their exoskeleton. This characteristic has been an important part of the evolution of ants as they allowed the ants to fight of any parasites. As a result, they were able to live longer and further support the nest.

However, some ants have lost this important gland but may be because they have moved their nests up into the trees, where they weave their nests with leaves instead of digging holes. On higher ground, there are fewer parasites and thus there is less selective advantage for having the metapleural gland. This means that ants, with or without the gland, have equal chances of survival and the gene for having the gland may mot be passed down as frequently as compared to ants on the ground. Furthermore, the loss of this gland may have well been supplemented by increased grooming and stronger venom, as recent studies suggest.

Most male ants also do not possess this gland although possible explanations include them sharing the secretions with their counterparts in the nest. Additionally, slavemaker ants (yes, some ants do enslave other ants) also do not have these glands. Instead they make use of the slaves to produce these secretions, since it is the slaves who groom the slavemakers.